#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int fib(int x)
{
	if (x == 1 || x == 2)
		return 1;
	else
		return fib(x - 1) + fib(x - 2);
}
int main()
{
	int i = 0;
	scanf("%d", &i);
	printf("%d", fib(i));
}